@lukasrosario/account/src/kms/crypto-key/index.ts

Base Account SDK

import { Hex, PublicKey, Signature, WebAuthnP256, WebCryptoP256 } from 'ox';
import { LocalAccount, OneOf, hashMessage, hashTypedData } from 'viem';
import { type WebAuthnAccount } from 'viem/account-abstraction';

import { createStorage } from './storage.js';

export type P256KeyPair = {
  privateKey: CryptoKey;
  publicKey: PublicKey.PublicKey;
};

// *****************************************************************
// Constants
// *****************************************************************
export const STORAGE_SCOPE = 'base-acc-sdk';
export const STORAGE_NAME = 'keys';

export const ACTIVE_ID_KEY = 'activeId';

// *****************************************************************
// Storage
// *****************************************************************
export const storage = createStorage(STORAGE_SCOPE, STORAGE_NAME);

// *****************************************************************
// Functions
// *****************************************************************
export async function generateKeyPair(): Promise<P256KeyPair> {
  const keypair = await WebCryptoP256.createKeyPair({ extractable: false });
  const publicKey = Hex.slice(PublicKey.toHex(keypair.publicKey), 1);

  await storage.setItem(publicKey, keypair);
  await storage.setItem(ACTIVE_ID_KEY, publicKey);

  return keypair;
}

export async function getKeypair(): Promise<P256KeyPair | null> {
  const id = await storage.getItem<string>(ACTIVE_ID_KEY);
  if (!id) {
    return null;
  }
  const keypair = await storage.getItem<P256KeyPair>(id);
  if (!keypair) {
    return null;
  }
  return keypair;
}

async function getOrCreateKeypair(): Promise<P256KeyPair> {
  const keypair = await getKeypair();
  if (!keypair) {
    const kp = await generateKeyPair();
    const pubKey = Hex.slice(PublicKey.toHex(kp.publicKey), 1);
    await storage.setItem(pubKey, kp);
    await storage.setItem(ACTIVE_ID_KEY, pubKey);
    return kp;
  }
  return keypair;
}

async function getAccount(): Promise<WebAuthnAccount> {
  const keypair = await getOrCreateKeypair();

  /**
   * public key / address
   */
  const publicKey = Hex.slice(PublicKey.toHex(keypair.publicKey), 1);

  const sign = async (payload: Hex.Hex) => {
    const { payload: message, metadata } = WebAuthnP256.getSignPayload({
      challenge: payload,
      origin: 'https://keys.coinbase.com',
      userVerification: 'preferred',
    });
    const signature = await WebCryptoP256.sign({
      payload: message,
      privateKey: keypair.privateKey,
    });
    return {
      signature: Signature.toHex(signature),
      raw: {} as unknown as PublicKeyCredential, // type changed in viem
      webauthn: metadata,
    };
  };

  return {
    id: publicKey,
    publicKey,
    async sign({ hash }) {
      return sign(hash);
    },
    async signMessage({ message }) {
      return sign(hashMessage(message));
    },
    async signTypedData(parameters) {
      return sign(hashTypedData(parameters));
    },
    type: 'webAuthn',
  };
}

export async function getCryptoKeyAccount(): Promise<{
  account: OneOf<WebAuthnAccount | LocalAccount> | null;
}> {
  const account = await getAccount();
  return {
    account,
  };
}

export async function removeCryptoKey(): Promise<void> {
  const keypair = await getKeypair();
  if (!keypair) {
    return;
  }
  await storage.removeItem(Hex.slice(PublicKey.toHex(keypair.publicKey), 1));
  await storage.removeItem(ACTIVE_ID_KEY);
}